The organization based the rankings on ozone pollution levels produced when heat and sunlight come into contact with pollutants from power plants, cars, refineries and other sources.

• 这个组织是按当热量，阳光同电厂，汽车，精炼厂，等其它源头释放出的污染物接触后说产生出臭氧污染的程度高低来排名。